Measuring arrangement, electric drive, hoisting machine and elevator system

ABSTRACT

A measuring arrangement, an electric drive and an elevator system are provided for determining the position and/or movement of the rotor of an electric machine. The measuring arrangement includes a magnetic band whose magnetic property is so implemented that it varies in the longitudinal direction of the band.

FIELD OF THE INVENTION

The present invention relates to the measurement of position and/ormovement and in particular to the measurement of the position and/ormovement of the rotor of an electric machine.

DESCRIPTION OF PRIOR ART

For motor torque adjustment, it is necessary to have informationregarding the position of a magnetic pole of the rotor. In addition, forthe adjustment of motor movement, feedback is needed about the rotarymotion of the rotor.

The position of a magnetic pole of the rotor has traditionally beendetected by means of an absolute sensor measuring position data, such asa resolver. The measuring accuracy of a resolver is fairly low.Moreover, the resolver, like other absolute sensors, generally has to bemounted on the motor shaft, which, due to the structure of the motor,may be a difficult task. An absolute sensor mounted on the shaft mayalso increase the axial length of the motor.

For the measurement of position data and/or movement, e.g. an opticalencoder is also used. However, the operation of an optical encoder iseasily disturbed e.g. due to impurities or smoke. In addition, theoptical encoder may be difficult to mount in conjunction with the motordue to lack of space.

OBJECT OF THE INVENTION

The object of the present invention is to solve some of theabove-mentioned problems. To this end, the invention discloses ameasuring arrangement as defined in claim 1 for the measurement of theposition and/or movement of the rotor of an electric machine, a hoistingmachine as defined in claim 10, an electric drive as defined in claim16, an elevator system as defined in claim 17 and an elevator system asdefined in claim 18. Preferred embodiments of the invention aredisclosed in the dependent claims.

In the measuring arrangement of the invention, rotor position and/ormovement data is read using a specific magnetic band. The measuringarrangement of the invention can be flexibly disposed in a desired placein the electric machine.

BRIEF DESCRIPTION OF THE INVENTION

The measuring arrangement of the invention comprises a magnetic band,the magnetic property of said magnetic band being implemented to bevariable in the longitudinal direction of the band. The magnetic band isattached to the rotating part of the electric machine, in such a waythat the magnetic band is fitted to circle around the rotational axis ofthe rotor. The measuring arrangement also comprises a reader whichsenses the aforesaid magnetic property varying in the longitudinaldirection of the magnetic band, said reader being mounted on astationary part of the electric machine in the immediate vicinity of themagnetic band. The magnetic band preferably has successive portionsfollowing each other in the longitudinal direction of the band, each twoof said successive portions having magnetic properties differing fromeach other. In one embodiment, the magnetic band has at least twoparallel channels, each one of said channels containing successiveportions following each other in the longitudinal direction of the band,and different parallel channels differ from each other in respect of thedisposition and/or frequency of occurrence of the said successiveportions following each other. Such an implementation makes it possibleto identify the direction of rotation of the band.

In a preferred embodiment of the invention, the magnetic band is placedon a substantially circular ring around the rotational axis of therotor.

In an embodiment of the invention, the magnetic fields generated by twosuccessive portions following each other in the longitudinal directionof the magnetic band differ from each other in respect of intensity. Inan embodiment of the invention, the magnetic fields generated by twosuccessive portions following each other in the longitudinal directionof the magnetic band are oriented in mutually opposite directions.

In an implementation of the invention, the intensity of the magneticfield produced by the magnetic band varies in the longitudinal directionof the band substantially sinusoidally. Such a solution is advantageouswhen absolute position is to be determined by means of the magneticband.

In a preferred embodiment of the invention, the reader is arranged toproduce a measurement signal on the basis of the magnetic propertyand/or change in the magnetic property of the magnetic band portionlocated in the immediate vicinity of the reader. The measuringarrangement preferably comprises a magnetic-band reading circuit, whichhas an input for the measurement signal produced by the aforesaid readersensing the magnetic property, and which reading circuit has an outputfor data representing the position and/or movement of the rotor of theelectric machine.

The rotating part of the hoisting machine of the invention comprises adrive sheave rotatably mounted on the body part of the hoisting machine.The hoisting machine also comprises a drive-sheave protection plate,which is secured to the body part of the hoisting machine. Thedrive-sheave protection plate extends from the body part of the hoistingmachine to the side of the drive sheave so that the drive sheave ishoused in the space remaining between the protection plate and the bodypart. The hoisting machine is provided with a measuring arrangement asdescribed above, in such manner that the magnetic band comprised in themeasuring arrangement is fitted in conjunction with the rotating part ofthe hoisting machine while the reader comprised in the measuringarrangement is fitted in conjunction with the drive-sheave protectionplate. The drive sheave is preferably hollow, and the magnetic band ispreferably fitted inside the hollow drive sheave. In this way, a verycompact hoisting machine is achieved, and the externaldimension/dimensions of the hoisting machine can be reduced. In apreferred embodiment of the invention, the drive sheave is supported onthe body part of the hoisting machine via a bearing. This bearing isheld in a bearing housing which rotates with the drive sheave and isintegrated in the same body with the drive sheave.

In an implementation, the bearing housing is fitted inside a hollowdrive sheave, and the bearing housing is provided with a machinedmounting surface for the magnetic band. The magnetic band can be secureddirectly to the mounting surface machined in the bearing housing;however, in a preferred embodiment of the invention, the magnetic bandis secured to a separate mounting ring and the mounting ring is securedto the mounting surface machined in the bearing housing.

The drive-sheave protection plate is secured to the body part of thehoisting machine by at least two different points to increase therigidity of the hoisting machine. Such a stiffening solution isadvantageous particularly in the case of a substantially flat hoistingmachine, whose total dimension in the axial direction is smaller thanthe total dimension of the hoisting machine in the radial direction.

The electric drive of the invention comprises an electric machine and afrequency converter for producing a variable-amplitude andvariable-frequency supply voltage for controlling the electric machine.Fitted in the electric machine is a measuring arrangement as describedabove for measuring the position and/or movement of the rotor of theelectric machine. The electric machine preferably comprises asynchronous motor. In a preferred embodiment of the invention, therotating part of the electric machine comprises a mounting surface madefor the magnetic band, which mounting surface revolves about therotational axis of the rotor, the distance of said mounting surface fromthe rotational axis of the rotor being substantially constant. In animplementation, a data transfer connection is provided between themagnetic band reader and the frequency converter for transmitting thedata representing the position and/or movement of the rotor of theelectric machine to the frequency converter.

The elevator system of the invention comprises an electric drive asdescribed above for controlling the movement of the elevator car. Anelevator control unit is arranged to determine the position of theelevator car in the elevator shaft, using for this determination thedata representing the movement and/or position of the rotor of theelectric machine obtained from the magnetic band reader.

The elevator system of the invention is implemented using a hoistingmachine as described above.

The magnetic band of the invention can preferably be fitted on theinside but also on the outside of the electric machine e.g. in a placethat is the most advantageous in respect of space-saving or ofstructural properties of the electric machine. Likewise, the point ofattachment of the reader relative to the magnetic band can be selectedflexibly, and the reader can be placed on the outside or on the insideof the electric machine.

In respect of reliability, measurement based on a magnetic field is moreadvantageous than e.g. optical measurement, because the passage of amagnetic field is not disturbed due to impurities or e.g. smoke in theway the passage of electromagnetic radiation is disturbed in measuringdevices based on optics. Also, the service life of the LEDs used inoptical sensors is quite limited, e.g. about 100 000 hours of usage.Moreover, the magnetic band of the invention can in many cases beimplemented as a fairly long band, because it can be fitted around therotational axis of the rotor on a circle of a substantially largerradius than would be possible if prior-art sensors were used. The largelength of the magnetic band makes it possible for the magnetic band tocomprise in the longitudinal direction of the band a large amount ofe.g. cyclically varying information. The large amount of informationused in the measurement improves the measuring accuracy of the magneticband.

The above summary as well as the additional features and advantages ofthe invention explained below will be better understood from thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail byreferring to embodiment examples, which in themselves are notrestrictive of the sphere of application of the invention, and to theattached drawings, wherein

FIGS. 1 a-1 c visualize a measuring arrangement according to theinvention

FIG. 2 visualizes the disposition of the measuring arrangement of theinvention

FIG. 3 visualizes an electric drive according to the invention

FIG. 4 visualizes an elevator system according to the invention

FIG. 5 visualizes a magnetic band according to the invention

FIG. 6 visualizes a hoisting machine according to the invention

FIG. 7 shows a magnetic-band mounting ring according to the invention asseen from two different directions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 a presents a side view of an elevator hoisting machine 2 with ameasuring arrangement 1 according to the invention fitted in it formeasuring the position and/or movement of the rotor 3 of the hoistingmachine 2. FIG. 1 b represents a magnetic band 4 comprised in themeasuring arrangement as seen in front view. FIG. 1 c presents a moredetailed view of a part of a magnetic band 4 according to the inventionand a reader 8 comprised in the measuring arrangement which senses themagnetic property of the magnetic band 4.

The magnetic band 4 is attached to the rotating part of the elevatorhoisting machine 2, to the circumference of the rotor 3. For thispurpose, the circumference of the rotor 3 is provided with a mountingsurface 11 for the magnetic band 4, which mounting surface 11 forms acircle around the rotational axis 7 of the rotor and whose distance fromthe rotational axis 7 of the rotor is substantially constant. Themagnetic band 4 is placed on the mounting surface 11 on a substantiallycircular ring 11 around the rotational axis 7 of the rotor. The magneticband 4 secured to the plane 11 preferably by gluing. The magnetic bandreader 8 is placed on a circuit board 13, and the reader 8 is attachedto a stationary body part 9 of the elevator hoisting machine 2, in theimmediate vicinity of the magnetic band 4.

As visualized in FIG. 1 c, the magnetic band 4 consists of two parallelchannels 10A, 10B, and each one of these channels comprises successiveportions 5A, 5B; 6A, 6B following each other in the longitudinaldirection of the band 4. The magnetic band 4 is so implemented that themagnetic fields produced by each two successive portions 5A, 5B; 6A, 6Bfollowing each other are mutually oppositely oriented. For this reason,the magnetic band comprises e.g. ferromagnetic material whose internalmagnetic moments have been oriented by means of an intensive externalmagnetic field in each two successive band 4 portions 5A, 5B; 6A, 6Bfollowing each other in mutually opposite directions. The successiveportions 5A, 5B; 6A, 6B could also be implemented e.g. in such mannerthat in each two successive portions 5A, 5B; 6A, 6B following each otherthe absolute values of the magnetic field intensity differ from eachother or that the magnetic field intensity is zero in one of the twosuccessive portions 5A, 5B; 6A, 6B.

In channel 10B, the frequency of occurrence of successive portions 6A,6B following each other is greater than the frequency of occurrence ofsuccessive portions 5A, 5B in channel 10A. The magnetic band reader 8has two measuring heads, the first one of which reads the successiveportions 5A, 5B following each other in the longitudinal direction ofthe band in the first channel 10A of the magnetic band while the secondone reads the successive portions 6A, 6B following each other in thelongitudinal direction of the band in the second channel 10B of themagnetic band. The reading function is here implemented using inductivecoils producing a measurement signal in which a pulse is detected eachtime when a change occurs in the magnetic field of the magnetic bandunder the coil. Instead of coils, the measuring head could also beimplemented using other sensors reacting to magnetic field, such as hallsensors or magneto-resistive sensors. The velocity of revolution of themagnetic band can be determined e.g. by calculating the time intervalbetween measurement signal pulses or the number of measurement signalpulses per unit of time. As the frequencies of occurrence of successiveportions 5A, 5B; 6A, 6B following each other in the channels 10A, 10B ofthe magnetic band differ from each other, it is possible, by comparingthe measurement signals of the coils reading different channels 10A,10B, to determine, besides the velocity of revolution of the magneticband 5, also the direction of revolution of the magnetic band 4 relativeto the magnetic band reader 8. A two-channel measurement signal likethis revealing the direction of revolution could also be implemented byplacing the successive portions following each other in differentchannels 10A, 10B of the magnetic band 4 so that they have a given phaseshift relative to each other, in which case the direction of revolutioncould be detected by comparing the phase shifts in the measurementsignals of the two channels 10A, 10B.

By providing the above-described magnetic band 4 with additionalchannels/successive portions, it is also possible to read the absoluteposition of the rotor 3 by means of the magnetic band. In addition, itis possible to include in the magnetic band one or more reference pointswhere the position and/or frequency of occurrence and/or magneticproperties of successive portions 5A, 5B; 6A, 6B of the magnetic band 4differ from the rest of the magnetic band. In this case, rotor positiondata is determined by integrating the pulses obtained from the magneticband reader, and the integrated position data is corrected at theaforesaid one or more reference points.

FIG. 5 represents a magnetic band according to an embodiment of theinvention, which comprises two parallel channels 10A, 10B. The intensityof the magnetic field produced by the magnetic band varies in bothchannels substantially sinusoidally in the longitudinal direction of theband. The intensity of the magnetic field is read from each channel 10A,10B e.g. by means of a magneto-resistive sensor or a hall sensor. Thus,two measurement signals varying sinusoidally in the longitudinaldirection of the magnetic band 4 are obtained. The cycle time 31 of thesinusoidal variation of the magnetic field is the same in both channels10A, 10B, but there is a 90-degree phase shift in the sinusoidalvariation of the magnetic field between the two channels. Thus, bycomparing the sinusoidal measurement signals of the two channels 10A,10B, it is possible to determine the position of the reader 8 relativeto the magnetic band 4 in the part of the magnetic band determined bythe cycle time 31 of the sinusoidal measurement signals. In anembodiment of the invention, the number of sinusoidally varying cyclesin the magnetic band has been selected to be the same as the number ofpole pairs in the motor.

FIG. 2 shows a sectional drawing of an elevator hoisting machine 2according to the invention, which comprises combinations of a magneticband 4 and a reader 8 e.g. according to the embodiment examplesvisualized in FIG. 1 and/or FIG. 5, placed in different parts. The motorin FIG. 2 is a permanent-magnet synchronous motor, in which thepermanent magnets are mounted on the rotor 3. The drive sheave 6 of theelevator is integrated with the rotor 3. The air gap between the stator22 and the rotor 3 is substantially parallel to the rotational axis 7 ofthe rotor. The rotor 3 and the drive sheave 6 are rotatably supported bybearings 27 on the body part of the hoisting machine. The bearing 27 ismounted in a bearing housing 34, which is integrated in the same bodywith the drive sheave 6.

The drive-sheave protection plate 28 secured to the body part 33 of thehoisting machine extends to the side of the drive sheave 6 so that thedrive sheave 6 is housed in the space remaining between the protectionplate 28 and the body part 33.

As appears from FIG. 2, the magnetic band reader 8 can be secured e.g.to the mounting frame 9 of the stator 22 or to the stationarydrive-sheave protection plate 28. The magnetic band 4 is fixed by gluingto the rotating part of the machine 2, so that the magnetic band 4revolves about the rotational axis 7 of the rotor. The magnetic band canbe disposed as shown in FIG. 2 e.g. so that the magnetic band 4 is readin a substantially horizontal or vertical direction. The magnetic band 4is preferably placed outside the magnetic circuit formed by the rotor 3,the stator 22 and the air gap between these, thus ensuring that themagnetic flux rotating in the motor will not disturb the measurement ofrotor position and/or movement.

FIG. 3 represents an electric drive 15 according to the invention,comprising an electric machine 2 and a frequency converter 16. Theelectric machine 2 comprises a synchronous motor. The frequencyconverter 16 contains a rectifier part 24 and an inverter part 23, whichcomprise electronic switches for supplying power from an alternatingpower source 25 to the synchronous motor 2. The rectifier part 24rectifies the constant-frequency alternating voltage from thealternating power source 25, producing a direct voltage to thedirect-voltage intermediate circuit of the frequency converter. Theinverter part 23 again converts the direct voltage of the direct-voltageintermediate circuit into a variable-amplitude and variable-frequencysupply voltage for controlling the synchronous motor 2. Fitted in theelectric machine 2 is a measuring arrangement according to theembodiment examples of e.g. FIG. 1 and/or FIG. 5 for measuring theposition and/or movement of the rotor of the electric machine.Therefore, a data transfer connection 17 is provided between thefrequency converter 16 and the magnetic band reader 8 attached to astationary part of the electric machine 2 to allow the data indicatingthe position and/or movement of the rotor of the electric machine 2 tobe passed to the frequency converter 16. The measuring arrangementcomprises a magnetic-band reading circuit 13, which has an input for thetwo-channel measurement signal 12 produced by the magnetic band reader8. The magnetic-band reading circuit 13 also has an output for data 14representing the position and/or movement of the rotor 3 of the electricmachine. The magnetic-band reading circuit 13 has been arranged toprocess the measurement signal 12 of the magnetic band reader in such away that the data 14 representing the position and/or movement of therotor 3 of the electric machine is converted into a form understandableto the controller 25 of the frequency converter 16. The said rotorposition and/or movement data 14 is used for both torque control andvelocity control of the frequency converter.

FIG. 6 visualizes an elevator hoisting machine according to theinvention in a simplified form. Except for the simplified formulation,the hoisting machine in FIG. 6 is mainly similar to the one illustratedin FIG. 2; however, FIG. 6 gives a more detailed illustration of thedisposition and securing of the drive-sheave protection plate 28 in thehoisting machine, among other things. FIG. 6 also visualizes thedisposition of the magnetic band 4 and reader 8 already illustrated inFIG. 2, but now as seen from another direction.

The rotating part of the hoisting machine comprises the drive sheave 6,which is supported by bearings on the body part 33 of the hoistingmachine. The axial total dimension of the hoisting machine is smallerthan the radial total dimension of the hoisting machine, so the hoistingmachine is substantially flat in the direction of the rotational axis ofthe hoisting machine. The drive-sheave protection plate 28 secured tothe body part 33 of the hoisting machine extends to the side of thedrive sheave 6, so that the drive sheave 6 is housed in the spaceremaining between the protection plate 28 and the body part 33. Thedrive-sheave protection plate 28 is secured by three different points 32to the body part of the hoisting machine to increase the rigidity of thehoisting machine. The magnetic band 4 comprised in the measuringarrangement of the invention is fitted in conjunction with the rotatingpart of the hoisting machine, and the reader 8 comprised in themeasuring arrangement is fitted in conjunction with the drive-sheaveprotection plate 28.

The bearing suspension has been implemented by mounting the bearing 27in a rotating bearing housing 34. The bearing housing 34, the drivesheave 6 and the rotor 3 are integrated in the same body. The bearinghousing 34 is fitted inside the hollow drive sheave 6. Machined in thebearing housing is a ledge with a mounting surface for the attachment ofthe magnetic band 4.

The hoisting machine in FIG. 6 differs from the hoisting machine in FIG.2 in that the magnetic band 4 is secured to a separate mounting ring 35according to FIG. 7, and the mounting ring is further secured to thebearing housing 34.

FIG. 4 represents an elevator system 18 with an electric drive 15 e.g.according to the embodiment example in FIG. 3 fitted in it forcontrolling the movement of the elevator car 19. In the elevator system18, an elevator car 19 and a counterweight are suspended in an elevatorshaft 21 by ropes running over the drive sheave of the elevator hoistingmachine 2. Here the elevator hoisting machine 2 is also placed in theelevator shaft 21, in the immediate vicinity of an elevator shaft wall.The elevator hoisting machine 2 is of a discoid and as flat a design aspossible, so that it takes up a minimal space in the direction ofmovement of the elevator car 19 in the elevator shaft 21. Space savinghas been achieved by replacing an absolute encoder fitted on the rotaryaxle of the hoisting machine 2 with a combination of a magnetic band andreader 8 according to the invention.

The elevator car 19 is moved in the elevator shaft 21 by the hoistingmachine 2. Power is supplied to the elevator hoisting machine 2 from theelectricity network 25 by a frequency converter 16. For the control ofthe torque and motion of the hoisting machine, the measurement signalfrom the magnetic band reader 8 is passed to the frequency converter 16over a data transfer connection 17 between the reader 8 and thefrequency converter 16.

An elevator control unit 20 calculates for the elevator car 19 thevelocity profile according to which the elevator car 19 is to be movedin the elevator shaft 21.

This is one of the reasons why the elevator control unit 20 needs knowthe position along the elevator shaft 21 at which the elevator car 19 islocated at each instant of time. In this embodiment of the invention,the elevator control unit 20 calculates the position of the elevator car19 in the elevator shaft by using for position calculation the dataobtained from the magnetic band reader 8 indicating the position and/ormovement of the rotor of the elevator hoisting machine. The elevator carposition calculated from the position and/or movement data of the rotorof the hoisting machine is corrected at the door zones of the elevatorshaft 21, using measurement data obtained from door zone sensors 30.

The invention has been described above with reference to a fewembodiment examples. It is obvious to a person skilled in the art thatthe invention is not exclusively limited to the embodiments describedabove, but that many other embodiments are possible within the scope ofthe inventive concept defined in the claims.

1. A measuring arrangement for the measurement of the position and/ormovement of the rotor of an electric machine, comprising: a magneticband, the magnetic property of said magnetic band being so implementedthat the magnetic property varies in a longitudinal direction of theband, wherein the magnetic band is attached to a rotating part of theelectric machine, so that the magnetic band is fitted to revolve about arotational axis of the rotor, and wherein the measuring arrangementcomprises a reader which senses the magnetic property varying in thelongitudinal direction of the magnetic band, said reader being mountedon a stationary part of the electric machine in the immediate vicinityof the magnetic band.
 2. The measuring arrangement according to claim 1,wherein the magnetic band has successive portions following each otherin the longitudinal direction of the band, each two of said successiveportions having mutually different magnetic properties.
 3. The measuringarrangement according to claim 1, wherein the magnetic band has at leasttwo parallel channels, each one of said channels containing successiveportions following each other in the longitudinal direction of the band,and wherein different parallel channels differ from each other inrespect of the disposition and/or frequency of occurrence of the saidsuccessive portions following each other.
 4. The measuring arrangementaccording to claim 1, wherein the magnetic band is placed on asubstantially circular ring around the rotational axis of the rotor. 5.The measuring arrangement according to claim 1, wherein the magneticfields generated by two successive portions following each other in thelongitudinal direction of the magnetic band differ from each other inrespect of intensity.
 6. The measuring arrangement according to claim 1,wherein the magnetic fields generated by two successive portionsfollowing each other in the longitudinal direction of the magnetic bandare oriented in mutually opposite directions.
 7. The measuringarrangement according to claim 1, wherein the intensity of the magneticfield generated by the magnetic band varies in the longitudinaldirection of the band substantially sinusoidally.
 8. The measuringarrangement according to claim 1, wherein the reader is arranged toproduce a measurement signal on the basis of the magnetic propertyand/or change in the magnetic property of the magnetic band portionlocated in the immediate vicinity of the reader.
 9. The measuringarrangement according to claim 1, wherein the measuring arrangementcomprises a magnetic-band reading circuit, which has an input for themeasurement signal produced by the reader sensing the magnetic property,and which reading circuit has an output for data representing theposition and/or movement of the rotor of the electric machine.
 10. Ahoisting machine, comprising: a rotating part comprising a drive sheaverotatably mounted on a body part of the hoisting machine; a drive-sheaveprotection plate, wherein the drive-sheave protection plate is securedto the body part of the hoisting machine and extends to a side of thedrive sheave, so that the drive sheave is housed in a space remainingbetween the protection plate and the body part; and the measuringarrangement according to claim 1, in such manner that the magnetic bandin the measuring arrangement is fitted in conjunction with the rotatingpart of the hoisting machine, while the reader in the measuringarrangement is fitted in conjunction with the drive-sheave protectionplate.
 11. The hoisting machine according to claim 10, wherein the drivesheave is hollow; hollow, and the magnetic band is fitted inside thehollow drive sheave.
 12. The hoisting machine according to claim 10,wherein the drive sheave is supported on the body part of the hoistingmachine via a bearing, and said bearing is mounted in a bearing housingintegrated in a same body with the drive sheave.
 13. The hoistingmachine according to claim 12, wherein the bearing housing is fittedinside the hollow drive sheave.
 14. The hoisting machine according toclaim 12, wherein the bearing housing is provided with a machinedmounting surface for the attachment of the magnetic band.
 15. Thehoisting machine according to claim 10, wherein the magnetic band isattached to a separate mounting ring.
 16. An electric drive comprising:an electric machine; and a frequency converter for producing avariable-amplitude and variable-frequency supply voltage for controllingthe electric machine, wherein the measuring arrangement according toclaim 1 is fitted in the electric machine for measuring the positionand/or movement of the rotor of the electric machine.
 17. An elevatorsystem, comprising the electric drive according to claim 16 forcontrolling the movement of the elevator car, wherein an elevatorcontrol unit is arranged to determine the position of the elevator carin the elevator shaft, using for this determination the data detected bythe magnetic band reader representing the movement and/or position ofthe rotor of the electric machine.
 18. An elevator system, characterizedin that the elevator system comprises a comprising the hoisting machineaccording to claim 10 for moving an elevator car in an elevator shaft.19. The measuring arrangement according to claim 2, wherein the magneticband has at least two parallel channels, each one of said channelscontaining successive portions following each other in the longitudinaldirection of the band, and wherein different parallel channels differfrom each other in respect of the disposition and/or frequency ofoccurrence of the said successive portions following each other.
 20. Themeasuring arrangement according to claim 2, wherein the magnetic band isplaced on a substantially circular ring around the rotational axis ofthe rotor.